Getting return undefined on recursive function javascript

Question

I heard recursive function is powerful so instead going through loop i tried to create a function which increments a number until it reach certain points. when it reaches i trie

Answer 1

rec will either return i (if i is over 100) or undefined (otherwise).

When you call it here:

console.log(rec());

i will be 1 so it will return undefined.

You never do anything with the return value when the return value is over 100.

You need to return the result of the recursive call:

} else {
    return rec();
}

so when it is over 100, the value gets passed back up the stack.

it this kind of recursion is good then for loop?

No. It is horribly inefficient.